.problem-list {
  width: 100%;
  padding: 20px;
  background: #fff;
  border-radius: 4px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.page-title {
  text-align: center;
  color: #333;
  font-size: 24px;
  margin: 0 0 20px;
  font-weight: 500;
}

.search-container {
  margin-bottom: 20px;
}

.problem-list .search-box {
  display: flex;
  align-items: center;
  max-width: 500px;
  margin: 0 auto;
  background: #f5f5f5;
  border: 1px solid #d9d9d9;
  border-radius: 4px;
  overflow: hidden;
  transition: all 0.3s;
}

.problem-list .search-box:hover,
.problem-list .search-box:focus-within {
  border-color: #1890ff;
  box-shadow: 0 0 0 2px rgba(24, 144, 255, 0.1);
}

.problem-list .search-box input {
  flex: 1;
  height: 40px;
  padding: 0 16px;
  border: none;
  font-size: 14px;
  background: #f5f5f5;
  outline: none;
  color: #333 !important;
  width: 100% !important;
}

.problem-list .search-box input::placeholder {
  color: #999;
}

.problem-list .search-box button {
  width: 40px;
  height: 40px;
  border: none;
  background: none;
  cursor: pointer;
  color: #999;
  transition: color 0.3s;
}

.problem-list .search-box button:hover {
  color: #1890ff;
}

table {
  width: 100%;
  border-collapse: collapse;
}

th, td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid #eee;
}

th {
  font-weight: 500;
  color: #333;
  background: #fafafa;
  white-space: nowrap;
}

td {
  color: #666;
}

.id-cell {
  width: 60px;
}

.title-cell {
  min-width: 200px;
}

.source-cell {
  width: 200px;
}

.pass-rate-cell {
  width: 100px;
}

.difficulty-cell {
  width: 100px;
}

.problem-title-link {
  color: #1890ff;
  text-decoration: none;
}

.problem-title-link:hover {
  text-decoration: underline;
}

.source-tag {
  display: inline-block;
  padding: 2px 8px;
  margin: 0 4px 4px 0;
  border-radius: 2px;
  background: #f5f5f5;
  color: #666;
  font-size: 12px;
}

.difficulty {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 2px;
  font-size: 12px;
}

.difficulty.简单 {
  background: #f6ffed;
  color: #52c41a;
  border: 1px solid #b7eb8f;
}

.difficulty.中等 {
  background: #fff7e6;
  color: #fa8c16;
  border: 1px solid #ffd591;
}

.difficulty.困难 {
  background: #fff1f0;
  color: #f5222d;
  border: 1px solid #ffa39e;
}

.difficulty-filter {
  margin: 20px 0;
  border: 1px solid #d9d9d9;
  border-radius: 2px;
  display: inline-flex;
  overflow: hidden;
}

.difficulty-btn {
  padding: 6px 16px;
  border: none;
  background: none;
  cursor: pointer;
  color: #666;
  font-size: 14px;
  transition: all 0.3s;
  position: relative;
}

.difficulty-btn:not(:last-child)::after {
  content: '';
  position: absolute;
  right: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 1px;
  height: 14px;
  background: #d9d9d9;
}

.difficulty-btn:hover {
  color: #1890ff;
  background: #f0f7ff;
}

.difficulty-btn.active {
  color: #1890ff;
  background: #e6f7ff;
}

.difficulty-tag {
  display: inline-block;
  padding: 2px 12px;
  border-radius: 2px;
  font-size: 12px;
  line-height: 20px;
  border: 1px solid;
}

.difficulty-tag.简单 {
  color: #52c41a;
  background: #f6ffed;
  border-color: #b7eb8f;
}

.difficulty-tag.中等 {
  color: #fa8c16;
  background: #fff7e6;
  border-color: #ffd591;
}

.difficulty-tag.困难 {
  color: #f5222d;
  background: #fff1f0;
  border-color: #ffa39e;
}

@media (max-width: 768px) {
  .problem-list {
    padding: 10px;
  }

  .problem-list .search-box {
    margin: 0 10px;
  }

  .source-cell,
  .pass-rate-cell {
    display: none;
  }
  
  .problem-title-link {
    font-size: 14px;
  }
  
  th, td {
    padding: 12px 8px;
  }
}
